1. Field of the Invention
The present invention relates to the reproduction of data recorded on an optical disc, and more particularly, to a method and apparatus which adjust a signal read from an optical disc in order to obtain stable binary data.
2. Description of the Related Art
Binary data is recorded on the surface of optical discs such as CDs (Compact Discs) or DVDs (Digital Versatile Discs). Recorded binary data can be reproduced by reading an optical signal obtained by reflecting a laser beam off the surface of an optical disc. The data recorded on optical discs is binary data, but the signals read from the optical discs are RF(Radio Frequency) signals, which are analog signals. Therefore, a process to convert RF signals into a digital signals is needed.
For restoration of data stored on an optical disc, a binary processing unit and a PLL (Phase Locked Loop) circuit are commonly used. The binary processing unit can include a sign detection circuit, a run length correction processor, or a Viterbi decoder. It is generally believed that binary processing units using Viterbi decoders are superior. However, the higher the recording density of the optical disc, the more frequent the data stored in the optical disc cannot be reproduced without error, even when using a Viterbi decoder.